A known method for connecting a semiconductor chip to a wiring board (mounting board) in a semiconductor device such as an IC or an LSI is to bond bumps provided on a surface of the semiconductor chip to terminals of the wiring board.
In recent years, there has been a demand for further microminiaturization of the semiconductor chip for size reduction of electronic apparatuses typified by mobile phones and PDA (personal digital assistants). With the microminiaturization of the semiconductor chip, the pitch of the bumps on the surface of the semiconductor chip is reduced to about 10 μm.
Further, known examples of a structure designed for size reduction and higher density integration of the semiconductor device include a chip-on-chip structure in which a semiconductor chip is bonded to a second semiconductor chip in face-to-face relation, and a flip chip bonding structure in which a semiconductor chip is bonded to a wiring board with its front surface being opposed to the wiring board.
In the semiconductor device having such a structure, bumps composed of a metal such as gold (Au) are provided on the surface of the semiconductor chip. The bumps are connected to bumps provided on the surface of the second semiconductor chip or electrode pads provided on the surface of the wiring board, whereby the semiconductor chip is bonded to the second semiconductor chip or the wiring board in predetermined spaced relation. In the bonding, an ACF (anisotropic conductive film) is interposed between the semiconductor chips or between the semiconductor chip and the wiring board. Thus, a space between the semiconductor chips or between the semiconductor chip and the wiring board is sealed with the ACF. Further, electrically conductive capsules contained in parts of the ACF present in junctures of the bumps are collapsed, whereby electrical connection between the bumps or between the bumps and the electrode pads is properly established.    Patent document 1: Japanese Unexamined Patent Publication No. 2003-297868    Patent document 2: Japanese Unexamined Patent Publication No. 2000-340595